Peregrine falcons are nesting atop high-rises. Coyotes are raising families in Golden Gate Park. There are plenty of raccoons tipping over trash cans, foxes trotting along hiking trails and possums living under porches.

Now a river otter has taken up residence in the brackish 19th century ruins of a swimming pool near the Cliff House. Who knows, maybe he'll be the advance guard of the next wave of deer, mountain lions and bears lurking a few freeway exits beyond the San Francisco city limits.

Mother Nature - or at least a hungry critter or two - is beating paths back to old haunts. It's a reminder that even a big city has natural appeal. Wildlife can prosper in the most overlooked and neglected spots.

In the latest case, an otter known as Sutro Sam has moved into the former oceanside plunge near the Land's End bath named after former Mayor Adolph Sutro.

Sam, like other urban wildlife, isn't exactly sticking to an all-natural diet. He's dining on once-captive goldfish that humans have dumped into the old pool over the years. It's the otter equivalent of Dumpster diving, and he's welcome to it.

If he likes life here, he could lure other otters to return and join him, otter-ologists think. That would mark a milestone for a mammal once hunted to near extinction for its slick fur. The abandoned pool, it turns out, might be the ultimate otter habitat, thanks to a seep of fresh water and the nearby ocean for an escape route. He's also not put off by nosy humans or curious dogs. Who needs the zoo with this guy cavorting around here?

The city should be happy with its latest arrival. Sam could be a wandering lost soul or the latest example of nature's refusal to give up and go away. Asphalt, traffic and crowds aren't the only features of urban life anymore.